Oral or nasal delivery of a medicament using an inhalation device is a particularly attractive method of drug administration as these devices are relatively easy for a patient to use discreetly and in public. As well as delivering medicament to treat local diseases of the airway and other respiratory problems, they have more recently also been used to deliver drugs to the bloodstream via the lungs thereby avoiding the need for hypodermic injections.
It is common for dry powder formulations to be pre-packaged in individual doses, usually in the form of capsules or blisters each of which contain a single dose of the powder that has been accurately and consistently measured. A blister is generally cold formed from a ductile, foil laminate or a plastics material and includes a puncturable or peelable lid which is heat-sealed around the periphery of the blister during manufacture and after introduction of the dose into the blister. A foil blister is preferred over a polymer blister or gelatine capsule as each dose is protected from the ingress of water and penetration of gases such as oxygen in addition to being shielded from light and UV radiation ail of which can have a detrimental effect on the delivery characteristics of the inhaler if a dose becomes exposed to them. Therefore, a blister offers excellent environmental protection to each individual drug dose.
It is known to provide an inhaler that is capable of holding a number of doses to enable it to be used repeatedly over a period of time without the requirement to open and/or insert a blister into the device each time it is used. Such a device is known from the Applicant's own earlier international application which has been published as WO 2005/037353 A1.
However, it is also desirable to provide a simple, low-cost unit-dose device that receives only one blister at a time. Once the dose contained in a blister has been inhaled, the blister is removed from the device and discarded by the patient. A fresh blister is then inserted into the device for a subsequent dose. This avoids the need for a strip indexing mechanism and so greatly simplifies the construction and operation of the device as well as reducing its overall dimensions.
A re-usable, unit-dose, passive dry powder inhaler for the delivery of medicinal products is known. The dose is pre-metered and contained in a foil blister to ensure the highest possible degree of protection for the drug together with reproducible dosing. The individual blister may be provided with a tab to enable a user to grasp it easily without damaging the dose containing cavity or blister bowl and to facilitate its insertion into the device and its subsequent removal therefrom after inhalation. Actuation of the device causes a piercing element to breach or rupture an inserted blister bowl so that when the patient inhales through the mouthpiece of the device, air is drawn through the blister to entrain the dose contained therein which is then carried out of the blister through the device and via the patient's airway down into the lungs.